Alien species — sometimes termed exotic, introduced or
non-native species — are plants and animals that have
been intentionally or unintentionally introduced, have
established populations and have spread into the wild in the
new host region (IUCN, 2002). In their home ranges, these
species live in balance with their local native environment,
and populations are controlled by ecosystem interactions
such as predation, parasitism and disease. However, once
they arrive in a new environment, they may become
established and invasive.